Preparation of high viscosity index lubricating oil

ABSTRACT

The viscosity index of a lubricating oil fraction is improved by treating the oil with a halogen, preferably chlorine, and then reacting the halogenated oil with an alpha olefin of from about 2 to 40 carbon atoms in the presence of an alkylation catalyst.

United States Patent [1 1 Favis [451 Jan. 21, 1975 PREPARATION OF HIGH VISCOSITY INDEX LUBRICATING OIL [75] Inventor: Dimitrios V. Favis, Sarnia, Ontario,

Canada [73] Assignee: Esso Research and Engineering Company [22] Filed: May 8, 1973 [21] Appl. N0.: 358,449

[52] US. Cl 208/46, 208/18 [51] Int. Cl Cl0g 41/00 [58] Field of Search 208/18, 46

[56] References Cited UNITED STATES PATENTS 2,130,024 9/1938 Pier et al. 208/18 Frey Axe Primary ExaminerHerbert Levine Attorney, Agent, or FirmByron O. Dimmick [57] ABSTRACT 6 Claims, No Drawings PREPARATION OF HIGH VISCOSITY INDEX LUBRICATING OIL BACKGROUND OF THE INVENTION This invention concerns the manufacture of a 1ubricating oil of high viscosity index. More particularly, it concerns the conversion of a lubricating oil base stock into a lubricating oil of higher viscosity index than the starting material by halogenating, preferably chlorinating, the lubricating oil base stock and then treating or reacting the halogenated material with an alpha olefin.

It has long been recognized that it is desirable that a lubricating oil have a high viscosity index, i.e., it is desirable that the lubricant undergo relatively small changes in viscosity with changes in temperature. The numerical value applied to the viscosity index in the lubricating art indicates the relation which the viscosity of a particular oil at 100F. bears to the viscosities of a representative Pennsylvania oil and a representative Coastal oil at 100F. where all three oils have the same viscosity at 210F. In this relationship, the Pennsylvania oil is considered to have a viscosity index of 100 and the Coastal oil a viscosity index of 0. Usually viscosity indexes are determined by the well known Dean and Davis method, which has been described in ASTM D- 567. For viscosity indexes higher than 100, it is preferred to use what is known as extended viscosity index, written as viscosity index and abbreviated as V.I. described in ASTM D-2270.

One method for raising the viscosity index of a lubricating oil base stock is to add a polymeric material known as a V.I. improver. In many instances, it is desirable to improve the viscosity index of a lubricating oil without resorting to the use of a VI. improving additive. The present invention provides one process for doing so.

DESCRIPTION OF THE PRIOR ART It is known in the art to manufacture a lubricating oil by the catalytic alkylation of a waste extract oil from lubricating oil refining, with a normal olefin of eight or more carbon atoms. This is taught, for example, in U.S. Pat. No. 2,554,395. It is also known to alkylate a lubricating oil base stock with a halogenated hydrocarbon in the presence of aluminum chloride. This is taught for example, in U.S. Pat. No. 2,010,387.

DESCRIPTION OF THE INVENTION In accordance with the present invention, a lubricating oil base stock having a viscosity index of less than 100 is converted into a lubricating oil base stock having a viscosity index of 120 or higher by first halogenating the starting base stock and then reacting it with an alpha olefin of from about 2 to about 40 carbon atoms, in the presence of an alkylation catalyst, such as aluminum chloride. Preferably the product thereby obtained is hydrogenated as a finishing step in order to remove residual halogen.

The starting lubricating oil base stocks that are employed in the process of this invention can be from paraffinic, naphthenic, coastal or mixed base crudes and are normally those having viscosities within the range of about 35 to 100 SUS at 210F. and viscosity indexes of the range of those found in conventionally refined lubricating oil base stocks, e.g., from about 50 to 95. The starting lubricating oil can contain some aromatic hydrocarbons, e.g., an aromatic hydrocarbon content of from about 10 to 50 percent, although aromatic-free stocks such as white oils can also be used. The starting base stock is halogenated with either bromine or chlorine, preferably the latter, using sufficient halogen to provide about 0.1 to 1 atom of halogen per mole of the oil. The halogenation step can be conducted in the liquid phase or the vapor phase using conventional procedures. For example the oil is chlorinated simply by passing chlorine gas through it, normally at a temperature of about to 180, e.g., at about to F. in the presence of light, e.g., tungsten light, at an injection rate of 0.5 to 1 gram of chlorine per 100 grams of oil per minute.

The halogenated lubricating oil base stock is then reacted with a linear alpha olefin of from about 2 to 40 carbon atoms, preferably about 8 to 24 carbon atoms and most preferably an olefin having from about 10 to 20 carbon atoms. This reaction is conveniently referred to as an alkylation reaction, although it should be realized that condensation, alkylation, polymerization and isomerization can occur simultaneously in this reaction. The proportion of olefin to oil in the alkylation reaction can range from about 20 to about 200 parts by weight of olefin per one hundred parts of the starting base stock, preferably from about 35 to about parts of olefin per one hundred parts of oil. This reaction is conducted in the presence of a suitable alkylation catalyst, preferably one of the acid type known as Friedel- Crafts catalysts, which include aluminum chloride, zinc chloride, boron trifluoride, aluminum bromide, etc. Preferably AlCl is used. The amount of catalyst used will ordinarily be within the range of about 1 to 100 wt. percent based on the weight of combined reactants. The reaction can be conducted at a temperature rang ing from the melting point to the boiling point of the mixture, e.g., 0 to 500F., more usually from ambient temperature to about 300F., preferably from about 100 to 250F. The time of the reaction will depend on reaction conditions and must be sufficient for its completion, which can be readily determined by the amount of heat evolved, as the reaction is exothermic. Usually the reaction will take from 1 to 2 hours. The reaction pressure will normally be atmospheric, although higher or lower pressures can be employed. The reaction can be conducted under an inert atmosphere such as one of nitrogen, but it is preferably conducted under a blanket of hydrogen halide. At the completion of the reaction, the mixture is washed with water to destroy the catalyst and remove water-soluble catalyst decomposition products. Any insoluble matter that is present is removed by filtration.

It is preferred to treat the alkylation product to remove residual halogen therefrom, and this is preferably done by hydrogenation using conventional procedures in the presence of conventional catalysts such as nickel or palladium, e.g., at 400F. and 800 psig over nickel. Also light ends can be removed by conventional fractionating procedures. In the examples given hereinafter the yields and properties given are for the lubricating oil portion of the products, i.e., after lighter materials were removed by stripping at 425F. under 10 mm mercury absolute pressure. If it is found desirable to reduce the pour point of the product this can be accomplished by conventional dewaxing procedures.

The olefins employed in the alkylation reaction of this invention are aliphatic terminal olefins having from about 2 to about 40 carbon atoms, e.g., n-l-hexene, n-leicosene, n-l-triacontene, more preferably about 8 to 24 carbon atoms and most preferably about 10 to about 20 carbon atoms, e.g., -n-l-decene, n-l-dodecene, n-loctadecene, and n-l-hexadecene. Sources of such olefins include the cracking of paraffin wax, the polymerization of other olefins, such as ethylene and the dehydration of alcohols. See, for example, Kirk-Othmer Encyclopedia of Chemical Technology (Second Edition) Volume 14, pp. 321-325. The olefins will frequently comprise mixtures; for example a cut of higher olefins obtained by the cracking of paraffin wax might contain 90 wt. percent of alpha olefins, 6 percent of other olefins, and 4% of saturated hydrocarbons, wherein the hydrocarbon range may cover from 20 to 28 carbon atoms while it might predominate in C hydrocarbons (93 percent).

The nature of this invention and the manner in which it can be practiced will be better understood when reference is made to the following examples, which include preferred embodiments.

EXAMPLE 1 A lubricating oil base stock of SAE 10 viscosity grade, which was a phenol-treated paraffin distillate having a viscosity of 156 SUS at 100F. and a viscosity index of 92 was treated with chlorine in the presence of tungsten light under conditions providing one atom of chlorine per average molecule of hydrocarbon in the base oil. The chlorination was conducted in the liquid phase at 123F. and under atmospheric pressure, using a chlorine injection rate of about 0.54 gram per 100 grams of oil per minute. The HCl evolved was blown through a predetermined amount of sodium hydroxide solution of known strength, the neutralization of which served to indicate attainment of the desired level of chlorination. Portions of the chlorinated lubricating oil were reacted separately with normal alpha-decene, normal alpha-hexadecene and normal alphaoctadecene, in each case using 52 wt. percent of olefin based on the monochlorinated lubricating oil distillate. The reactions were carried out at F. in the presence of wt. percent of aluminum chloride based on the combined reactants. The products were then hydrogenated over nickel catalyst in a conventional manner. The extended viscosity index V.1. ,of the base oil was increased from 97 to 108 with n-l-decene, to 124 with n-l-hexadecene and to 131 with n-l-octadecene.

" EXAMPLE 2 TABLE 1 Yield Wt. Olefin on Total Viscosity Reacted Charge 100F. 210F. v.1

n-l-Hexadecene 88 703 86.8 132 n-l-Octadecene 93 522 76.4 143 Starting oil had V.l. of 92 and viscosity of 156 SUS at 100F.

EXAMPLE 3 Time in Minutes PerCent Chlorine The chlorinated oils containing 3.3 percent chlorine and 10.3 percent chlorine were each alkylated with normal alpha-octadecene using respectively 1.60 and 1.94 moles of olefin per gram atom of chlorine in the LII chlorinated oil. Alkylation was conducted at 200F. for -125 minutes in the presence of 10 wt. percent of AlCl based on total reactants. The weight percentages of alpha-octandecene based on chlorinated lubricating oil were 38 percent and 142 percent respectively. The properties of the lubricating oil fraction of the alkylation products before and after hydrogenation (400F., 800 psig, nickel catalyst) are shown-in Table 11 which follows:

TABLE 11 Properties of Alkylate Wt. CI in Chlorinated Lube Oil Before Hydrogenation SUS Yield of Viscosity Alkylate 100F. 210F. V1

After Hydrogenation SUS Viscosity Pour 100F. 210F. v.1 Point "F.

The products of this invention are useful wherever a high viscosity index hydrocarbon lubricating oil base stock is desired, including the formulation of automotive crankcase lubricants, hydraulic oils, automatic transmission fluids, and so on.

It should be noted that the processes of alkylation, water wash, filtration, and hydrogenation were often facilitated by dilution with an inert solvent such as nheptane, etc.

The foregoing examples are by way of illustration only and numerous variations thereof are possible within the scope of the invention as defined by the claims.

What is claimed is:

l. A process for increasing the viscosity index of a petroleum hydrocarbon lubricating oil base stock having a viscosity within the range of 35 to 100 SUS at 210F.

5 and an original viscosity index of about 50 to 95 which comprises the steps of halogenating the said base stock to the extent of from 0.1 to 1 atom of halogen per average molecule of said base stock, and thereafter reacting 4. Process as defined by claim 1 wherein said catalyst is aluminum chloride.

5. Process as defined by claim 1 wherein said linear olefin has from 8 to 24 carbon atoms.

6. Process as defined by claim 1 wherein from 35 to wt. percent of linear alpha olefin is reacted with the halogenated base stock. 

2. A process as defined by claim 1 wherein said linear alpha olefin has from about 10 to about 20 carbon atoms.
 3. A process as defined by claim 1 wherein said base stock is treated with chlorine as the halogen.
 4. Process as defined by claim 1 wherein said catalyst is aluminum chloride.
 5. Process as defined by claim 1 wherein said linear olefin has from 8 to 24 carbon atoms.
 6. Process as defined by claim 1 wherein from 35 to 150 wt. percent of linear alpha olefin is reacted with the halogenated base stock. 